Pressure-Treated Wood Decking Calculator: How Many Boards Do I Need? (2026 Cost Guide)
Budget-friendly southern yellow pine decking treated against rot and insects.
Pressure-treated (PT) decking is the most affordable deck surface in North America. 5/4×6 radius-edge boards are 5.5 inches wide and about 1 inch thick; 2×6 boards are thicker and span farther. PT lumber is often sold wet from treatment — boards butted tight will shrink and open a gap of about 1/8" as they dry.
1Measure the space
2Board size & layout
Recommended: 10% for straight/offset, 15% for diagonal & herringbone.
3Packaging & price
Your Pressure-Treated Wood Decking estimate
Area incl. waste
211.2 sq. ft
boards needed
29
Purchase
29 boards
Material cost
$585
- DIY — materials only$585
- Installation labor (pro)$960 – $1,920
- Hire a pro — total installed$1,545 – $2,505
Labor at $5–$10 per sq. ft (US average). Doing it yourself saves roughly $960–$1,920.
Material shopping list
| Pressure-Treated Wood Decking (5 1/2" × 192")212.7 sq. ft of coverage | 29 boards |
| Hidden fastener boxes (≈ 50 sq. ft each) | 4 boxes |
| Color-matched screws for board endsPlus fascia boards and end caps if needed | 1 box |
192 sq. ft · Straight / Grid · 10% waste. Buy all boards from the same lot.
How many boards do I need? Quick-reference table
Based on 5 1/2" × 192" boards with 1/8" joints and $2.75/sq. ft material. "Straight / Grid" uses 10% waste; diagonal/herringbone uses 15%.
| Size | Area + 10% | boards | boards @ 15% | Material | Installed (pro) |
|---|---|---|---|---|---|
| 10×10 ft (100 sq. ft) | 110 sq. ft | 15 | 16 | $303 | $803–$1,303 |
| 12×12 ft (144 sq. ft) | 158.4 sq. ft | 22 | 23 | $444 | $1,164–$1,884 |
| 16×12 ft (192 sq. ft) | 211.2 sq. ft | 29 | 30 | $585 | $1,545–$2,505 |
| 20×16 ft (320 sq. ft) | 352 sq. ft | 47 | 50 | $948 | $2,548–$4,148 |
| 20×20 ft (400 sq. ft) | 440 sq. ft | 59 | 62 | $1,190 | $3,190–$5,190 |
The pressure-treated wood decking formula, step by step
- Measure the area. Multiply length × width in feet. Measure each section separately and add them for L-shapes.
- Add waste. Add 10% for straight or offset layouts and 15% for diagonal or herringbone.
- Find coverage per board. (board length + joint) × (board width + joint) ÷ 144 = sq. ft per board.
- Count boards. Divide the area including waste by the coverage per board and round up.
- Order full lengths. Order whole boards; choose a length that spans the area to minimize butt joints.
Worked example — a 16 × 12 ft area is 192 sq. ft. Adding 10% gives 211.2 sq. ft. Each 5 1/2" × 192" board with a 1/8" joint covers 7.505 sq. ft, so you need 29 boards.
Pressure-Treated Wood Decking cost guide (2026)
- Material: $2.00–$4.50 per sq. ft (calculator default $2.75).
- Professional labor: $5–$10 per sq. ft. Labor to install deck boards over an existing frame. New pressure-treated decks with framing typically run $15–$35 per sq. ft installed.
- Typical 16×12 project: $585 DIY vs. $1,545–$2,505 professionally installed.
Pro tips for pressure-treated wood decking
- If boards are still wet from treatment, install them tight; they'll shrink to a natural gap as they dry.
- Use hot-dip galvanized or coated deck screws rated for ACQ/CA treated lumber.
- Place boards bark-side (growth rings curving up) to reduce cupping.
- Wait 1–3 months before staining or sealing so the wood can dry out.
Pressure-Treated Wood Decking FAQ
How many 5/4×6 boards do I need for a 12×16 deck?
Using 16 ft boards with a 1/8" gap, a 12×16 ft deck needs about 26 boards, or 29 after a 10% waste allowance for trimming and defects.
Should pressure-treated deck boards be gapped?
Kiln-dried-after-treatment (KDAT) boards should be gapped 1/8"–3/16". Wet boards fresh from the yard should be installed tight because they will shrink as they dry.
Is 5/4 or 2×6 better for decking?
5/4×6 boards are cheaper and smoother but need 16" joist spacing. 2×6 boards can span 24" joists and feel stiffer underfoot, but they're heavier and cost more.
How much extra decking should I buy?
Add 10% for straight layouts and 15% for diagonal layouts. With PT lumber it also pays to pick through the pile and reject badly warped or split boards.